Instrumented sphere method for measuring thermal pressure in fluids and isotropic stresses and reaction kinetics in thermosetting resins

Merzlyakov, Mikhail; Meng, Yan; Simon, Sindee L.; McKenna, Gregory B.

doi:10.1063/1.1790584

Cited by 9 publications

(7 citation statements)

References 18 publications

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“…10 Recently, a novel technique was developed in our laboratories to measure the thermal pressure coefficient of thermosetting resins during cure and thermal cycling using an instrumented pressure vessel. [11][12][13] In that work, we found that the thermal pressure coefficient of the liquid monomer was higher than that of the glassy polymer 13 but we did not measure the property as a function of temperature or resin structure.…”

Section: Introductionmentioning

confidence: 97%

Viscoelastic properties and residual stresses in polyhedral oligomeric silsesquioxane‐reinforced epoxy matrices

Hutcheson

McKenna

et al. 2008

J Polym Sci B Polym Phys

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Fiber-filled thermosetting polymer composites are extensively used in aerospace industries. One disadvantage of these materials is cure induced or thermally induced residual stresses in the matrix, which may result in deteriorated performance and premature failure. This article explores the use of epoxy/multifunctional polyhedral oligomeric silsesquioxane (POSS) nanocomposites as resins with reduced thermal stress coefficients that result in mitigated residual stresses. The effect of POSS loading on the thermal stress coefficient of the epoxy/POSS nanocomposite resins was investigated from below the b-relaxation to the a-relaxation, or glass transition temperature, (i.e., from À100 to 180 C) by measuring the shear modulus and linear thermal expansion coefficient. The thermal stress coefficient of the epoxy/POSS nanocomposites is found to be a strong function of temperature, decreasing rapidly with decreasing temperature through the a-relaxation region, increasing in the vicinity of the b-relaxation, and then decreasing below the temperature associated with the peak in the b-relaxation. With increasing POSS content, the thermal stress coefficient is reduced compared with the neat resin in the vicinity of the a-relaxation; however, the thermal stress coefficient increases with increasing POSS content below the temperature of the b-relaxation peak.

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Section: Introductionmentioning

confidence: 97%

Viscoelastic properties and residual stresses in polyhedral oligomeric silsesquioxane‐reinforced epoxy matrices

Hutcheson

McKenna

et al. 2008

J Polym Sci B Polym Phys

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“…10. The filling procedure is similar to that used to fill spherical vessels 8 and involves evacuation of the air from the tube and filling liquid resin at 100°C in vacuum.…”

Section: Measurements During Thermoset Curementioning

confidence: 99%

“…8 The measured ␥ app was determined by fitting the stress/temperature curve in Fig. 5͑a͒ by a second order polynomial in the temperature range from 50 to 150°C and taking the temperature derivative of that fit, which results in a straight line in the ␥ app temperature dependence.…”

Section: B Thermal Pressure Of Known Fluidmentioning

confidence: 99%

Instrumented thick-walled tube method for measuring thermal pressure in fluids and isotropic stresses in thermosetting resins

Merzlyakov

Simon

McKenna

2005

Review of Scientific Instruments

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We have developed a method for measuring the thermal pressure coefficient and cure-induced and thermally induced stresses based on an instrumented thick-walled tube vessel. The device has been demonstrated at pressures up to 330 MPa and temperatures to 300 °C. The method uses a sealed stainless steel thick-walled tube to impose three-dimensional isotropic constraints. The tube is instrumented with strain gauges in hoop and in axial directions and can be used in open or closed configurations. By making measurements of the isotropic stresses as a function of temperature, the method allows determination of the thermal pressure coefficient in both the glassy and rubbery (or liquid) states. The method also can be used to measure isotropic stress development in thermosetting resins during cure and subsequent thermal cycling. Experimental results are presented for sucrose benzoate, di-2-ethylhexylsebacate, and an epoxy resin. The current report shows that the method provides reliable estimates for the thermal pressure coefficient. The thermal pressure coefficient is determined with resolution on the order of 10kPa∕K. Among advantages of the method is that the tubes are reusable, even when measurements are made for cure response of thermosetting resins.

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“…Several methods have been developed to measure the cure stress buildup for thermosetting polymers. These include beam‐bending technique,7,8 steel ring method,9 thin‐walled tube,10–11 thick‐walled tube,12 instrumented sphere method,13 etc. However, the above methods cannot measure the cure stresses directly, and cure stresses have to be computed on the basis of measured strain or deflection value.…”

Section: Introductionmentioning

confidence: 99%

Direct Measurement of Cure‐Induced Stress in Thermosetting Materials by Means of a Dynamic Mechanical Analyzer

Hónɡ

Mhaisalkar

Wong

2006

Macromol. Rapid Commun.

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Summary: Significant stresses develop during cure in functional and structural applications of polymeric materials ranging from glass fiber composites to advanced functional polymers used in microelectronics, optoelectronics, and biomaterials applications. These stresses arise from a combination of chemical shrinkage and stiffness buildup in a confined geometry. In this paper, a new method for direct measurement of cure‐induced stresses during curing of thermosetting materials by using the iso‐strain mode of a dynamic mechanical analyzer (DMA) has been developed. A thermal tape was used to facilitate maintaining a constant strain and initiate the iso‐strain measurement. Two quartz rods with a small gap were used to contain the material. The top of the quartz rod and one side of the thermal tape were secured by the fixed clamp, while the bottom quartz rod and the other side of the thermal tape were clamped with the moveable force probe. The cure force was thereby directly measured by the probe during the curing process. The cure stress buildup was observed to occur after a certain duration that corresponds to the gel point. Experimental results clearly show that curing at lower temperature could lead to higher cure stress due to the earlier onset of vitrification. An investigation of the stress buildup as a function of degree of cure indicates that a majority of the cure stress was generated in the vitrification regime. The methodology proposed herein provides an accurate experimental approach to investigate the cure‐induced stress generated in a thermosetting material in applications ranging from microelectronics and optoelectronics packaging to biomaterials amongst others.

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Instrumented sphere method for measuring thermal pressure in fluids and isotropic stresses and reaction kinetics in thermosetting resins

Cited by 9 publications

References 18 publications

Viscoelastic properties and residual stresses in polyhedral oligomeric silsesquioxane‐reinforced epoxy matrices

Viscoelastic properties and residual stresses in polyhedral oligomeric silsesquioxane‐reinforced epoxy matrices

Instrumented thick-walled tube method for measuring thermal pressure in fluids and isotropic stresses in thermosetting resins

Direct Measurement of Cure‐Induced Stress in Thermosetting Materials by Means of a Dynamic Mechanical Analyzer

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